<html>
    <head>
        <style type="text/css">
        div{background-color: #fc0;border-style: none;height: 50px;width:50px;}
        #back{position:absolute;top:0;right:0;bottom:0;left:0;background-color: #ccc;height: 200px;width:400px;margin: auto;}
        #circle-left{position: absolute;top:0;left:0;}
         #circle-right{position: absolute;bottom:0;right:0;}
        </style>
    </head>
    <body>
        <div id="back">
            <div id="circle-left">
                
            </div>
            <div id="circle-right">
            </div>
        </div>
    </body>
</html>